Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for cleaning semiconductor substrates, and more specifically, to a stiction-free cleaning and/or drying process for high-aspect-ratio semiconductor device structures.
Description of the Related Art
In the cleaning of semiconductor devices, it is necessary to remove liquid and solid contaminants from surfaces of a substrate, thus leaving clean surfaces. Wet cleaning processes generally involve the use of cleaning liquids, such as aqueous cleaning solutions. After wet cleaning the substrate, it is necessary to remove the cleaning liquid from the surface of the substrate in a cleaning chamber.
Most current wet cleaning techniques utilize a liquid spraying or immersion step to clean the substrate. Drying of the substrate that has high aspect ratio features or low-k materials which have voids or pores is very challenging subsequent to the application of a cleaning liquid. Capillary forces of the cleaning liquid often cause deformation of materials in these structures which can create undesired stiction, which can damage the semiconductor substrate in addition to leaving residue on the substrate from the cleaning solution utilized. The aforementioned drawbacks are especially apparent on substrates with high-aspect-ratio semiconductor device structures during subsequent drying of the substrate. Line stiction, or line collapse, results from bending of the side walls, which form the high-aspect-ratio trench or via, towards each other due to capillary pressure across the liquid-air interface over the liquid trapped in the trench or via during the wet cleaning process(es). Features with narrow line width and high-aspect-ratios are especially susceptible to the difference in surface tension created between liquid-air and liquid-wall interfaces due to capillary pressure, which is also sometimes referred to as capillary force. Current workable drying practices are facing a steeply rising challenge in preventing line stiction as a result of rapid device scaling advancements.
As a result, there is a need in the art for drying processes which reduce or eliminate line stiction that can reduce the semiconductor device yield on a substrate.